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Message-ID: <alpine.LFD.2.00.1110031753090.4447@dhcp-27-109.brq.redhat.com>
Date: Mon, 3 Oct 2011 18:00:12 +0200 (CEST)
From: Lukas Czerner <lczerner@...hat.com>
To: Yongqiang Yang <xiaoqiangnk@...il.com>
cc: linux-ext4@...r.kernel.org, jack@...e.cz, jeff.liu@...cle.com,
achender@...ux.vnet.ibm.com, adityakali@...gle.com
Subject: Re: [RFC PATCH V2 6/6] ext4: reimplement fiemap on delayed extent
tree
On Thu, 29 Sep 2011, Yongqiang Yang wrote:
> This patch reimplements fiemap on delayed extent tree.
>
> Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.com>
> ---
> fs/ext4/extents.c | 186 +++++++----------------------------------------------
> 1 files changed, 23 insertions(+), 163 deletions(-)
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index bdbb984..c2ae125 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3909,193 +3909,53 @@ static int ext4_ext_fiemap_cb(struct inode *inode, ext4_lblk_t next,
> struct ext4_ext_cache *newex, struct ext4_extent *ex,
> void *data)
> {
> + struct delayed_extent de;
> __u64 logical;
> __u64 physical;
> __u64 length;
> __u32 flags = 0;
> + ext4_lblk_t next_del;
> int ret = 0;
> struct fiemap_extent_info *fieinfo = data;
> unsigned char blksize_bits;
>
> - blksize_bits = inode->i_sb->s_blocksize_bits;
> - logical = (__u64)newex->ec_block << blksize_bits;
> + de.start = newex->ec_block;
> + down_read(&EXT4_I(inode)->i_data_sem);
> + next_del = ext4_de_find_extent(inode, &de);
> + up_read(&EXT4_I(inode)->i_data_sem);
>
> + next = min(next_del, next);
> if (newex->ec_start == 0) {
> /*
> * No extent in extent-tree contains block @newex->ec_start,
> * then the block may stay in 1)a hole or 2)delayed-extent.
> - *
> - * Holes or delayed-extents are processed as follows.
> - * 1. lookup dirty pages with specified range in pagecache.
> - * If no page is got, then there is no delayed-extent and
> - * return with EXT_CONTINUE.
> - * 2. find the 1st mapped buffer,
> - * 3. check if the mapped buffer is both in the request range
> - * and a delayed buffer. If not, there is no delayed-extent,
> - * then return.
> - * 4. a delayed-extent is found, the extent will be collected.
> */
> - ext4_lblk_t end = 0;
> - pgoff_t last_offset;
> - pgoff_t offset;
> - pgoff_t index;
> - pgoff_t start_index = 0;
> - struct page **pages = NULL;
> - struct buffer_head *bh = NULL;
> - struct buffer_head *head = NULL;
> - unsigned int nr_pages = PAGE_SIZE / sizeof(struct page *);
> -
> - pages = kmalloc(PAGE_SIZE, GFP_KERNEL);
> - if (pages == NULL)
> - return -ENOMEM;
> -
> - offset = logical >> PAGE_SHIFT;
> -repeat:
> - last_offset = offset;
> - head = NULL;
> - ret = find_get_pages_tag(inode->i_mapping, &offset,
> - PAGECACHE_TAG_DIRTY, nr_pages, pages);
> -
> - if (!(flags & FIEMAP_EXTENT_DELALLOC)) {
> - /* First time, try to find a mapped buffer. */
> - if (ret == 0) {
> -out:
> - for (index = 0; index < ret; index++)
> - page_cache_release(pages[index]);
> - /* just a hole. */
> - kfree(pages);
> - return EXT_CONTINUE;
> - }
> - index = 0;
> -
> -next_page:
> - /* Try to find the 1st mapped buffer. */
> - end = ((__u64)pages[index]->index << PAGE_SHIFT) >>
> - blksize_bits;
> - if (!page_has_buffers(pages[index]))
> - goto out;
> - head = page_buffers(pages[index]);
> - if (!head)
> - goto out;
> -
> - index++;
> - bh = head;
> - do {
> - if (end >= newex->ec_block +
> - newex->ec_len)
> - /* The buffer is out of
> - * the request range.
> - */
> - goto out;
> -
> - if (buffer_mapped(bh) &&
> - end >= newex->ec_block) {
> - start_index = index - 1;
> - /* get the 1st mapped buffer. */
> - goto found_mapped_buffer;
> - }
> -
> - bh = bh->b_this_page;
> - end++;
> - } while (bh != head);
> -
> - /* No mapped buffer in the range found in this page,
> - * We need to look up next page.
> - */
> - if (index >= ret) {
> - /* There is no page left, but we need to limit
> - * newex->ec_len.
> - */
> - newex->ec_len = end - newex->ec_block;
> - goto out;
> - }
> - goto next_page;
> - } else {
> - /*Find contiguous delayed buffers. */
> - if (ret > 0 && pages[0]->index == last_offset)
> - head = page_buffers(pages[0]);
> - bh = head;
> - index = 1;
> - start_index = 0;
> - }
> -
> -found_mapped_buffer:
> - if (bh != NULL && buffer_delay(bh)) {
> - /* 1st or contiguous delayed buffer found. */
> - if (!(flags & FIEMAP_EXTENT_DELALLOC)) {
> - /*
> - * 1st delayed buffer found, record
> - * the start of extent.
> - */
> - flags |= FIEMAP_EXTENT_DELALLOC;
> - newex->ec_block = end;
> - logical = (__u64)end << blksize_bits;
> - }
> - /* Find contiguous delayed buffers. */
> - do {
> - if (!buffer_delay(bh))
> - goto found_delayed_extent;
> - bh = bh->b_this_page;
> - end++;
> - } while (bh != head);
> -
> - for (; index < ret; index++) {
> - if (!page_has_buffers(pages[index])) {
> - bh = NULL;
> - break;
> - }
> - head = page_buffers(pages[index]);
> - if (!head) {
> - bh = NULL;
> - break;
> - }
> -
> - if (pages[index]->index !=
> - pages[start_index]->index + index
> - - start_index) {
> - /* Blocks are not contiguous. */
> - bh = NULL;
> - break;
> - }
> - bh = head;
> - do {
> - if (!buffer_delay(bh))
> - /* Delayed-extent ends. */
> - goto found_delayed_extent;
> - bh = bh->b_this_page;
> - end++;
> - } while (bh != head);
> - }
> - } else if (!(flags & FIEMAP_EXTENT_DELALLOC))
> - /* a hole found. */
> - goto out;
> -
> -found_delayed_extent:
> - newex->ec_len = min(end - newex->ec_block,
> - (ext4_lblk_t)EXT_INIT_MAX_LEN);
> - if (ret == nr_pages && bh != NULL &&
> - newex->ec_len < EXT_INIT_MAX_LEN &&
> - buffer_delay(bh)) {
> - /* Have not collected an extent and continue. */
> - for (index = 0; index < ret; index++)
> - page_cache_release(pages[index]);
> - goto repeat;
> + if (de.len == 0)
> + /* A hole found. */
> + return EXT_CONTINUE;
> +
> + if (de.start > newex->ec_block) {
> + /* A hole found. */
> + newex->ec_len = min(de.start - newex->ec_block,
> + newex->ec_len);
> + return EXT_CONTINUE;
> }
>
> - for (index = 0; index < ret; index++)
> - page_cache_release(pages[index]);
> - kfree(pages);
> + flags |= FIEMAP_EXTENT_DELALLOC;
> + newex->ec_len = de.start + de.len - newex->ec_block;
> }
>
> - physical = (__u64)newex->ec_start << blksize_bits;
> - length = (__u64)newex->ec_len << blksize_bits;
> -
> if (ex && ext4_ext_is_uninitialized(ex))
> flags |= FIEMAP_EXTENT_UNWRITTEN;
>
> if (next == EXT_MAX_BLOCKS)
> flags |= FIEMAP_EXTENT_LAST;
As we know now, it is not enough to check for next allocated extent,
we also have to check that there is not any delayed extents after
this one.
Just now I have noticed this lines at the beginning of the function:
next_del = ext4_de_find_extent(inode, &de);
...
next = min(next_del, next);
which takes care of that, so it seems that it will fix both problems,
setting FIEMAP_EXTENT_LAST for the last extent in the file and taking
care of delayed extents as well.
The patch seems fine.
Thanks!
-Lukas
>
> + blksize_bits = inode->i_sb->s_blocksize_bits;
> + logical = (__u64)newex->ec_block << blksize_bits;
> + physical = (__u64)newex->ec_start << blksize_bits;
> + length = (__u64)newex->ec_len << blksize_bits;
> +
> ret = fiemap_fill_next_extent(fieinfo, logical, physical,
> length, flags);
> if (ret < 0)
>
--
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